The present invention resides in a multilayered hollow plastic article and method for obtaining same wherein the article may have two, three or more layers.
Multilayered hollow plastic articles are well known in the art wherein the article includes an inside film-like thermoplastic material and an outside pressure molded thermoplastic material. For example, thin-formed liners were heretofore made as by vacuum forming from a sheet of thermoplastic material to cover the entire inside surface of the preform and indeed to overlap the rim. The outside structural portion of the multilayered article is formed as by injection molding. Reference should be had to U.S. Pat. No. 3,717,544 to Valyi which discloses a method and apparatus for making lined plastic containers in which a liner is placed over a blow core, a plastic material is injected around the blow core and liner in an injection mold and the injected material together with the liner is blown in a blow mold. In accordance with the procedure of the '544 patent, the liners may be preformed and inserted over the blow core before the blow core is placed in the injection mold.
Different materials are used for the liner and the injected portion, respectively, in order to provide a combination of properties in the finished product that a single plastic lacks, for example, permeation resistance to fluids and strength, at modest cost. Typically, permeation resistant plastics, such as PEN, EVOH and PVDC, and others, are too expensive for packaging containers if used as a single layer.
Thus, the liner material may be made of a barrier material such as polyethylene naphthalate (PEN) or other barrier material, and the outside may be made of a less expensive thermoplastic material such as polyethylene terephthalate (PET). Naturally, the expensive inside barrier material is considerably thinner than the less expensive outside thermoplastic material, typically less than ten percent (10%) of the total thickness.
However, it is not necessary to extend the expensive barrier material all the way to the rim of the multilayered article because this represents a waste of material as the neck of the multilayered article is generally too thick to transmit gas, and so is part of the shoulder. Also, the shorter the liner or sleeve, the better its L/D ratio and the easier and more economical it is to thermoform same because the skeleton scrap is reduced with decreasing depth of the draw.
In addition, application of liners in multicavity preform molds is generally one at a time and generally involves liners which extend all the way to the rim of the desired multilayered article. In general practice, the liners are thermoformed, trim-cut from a web, and transferred one at a time to the injection mold.
U.S. Pat. No. 3,954,923 to Valyi forms a multilayered liner material on a web wherein the liner extends to the rim of the desired multilayered article. Although the liners may be transferred to the injection molds on the web, the liners are made to cover the entire inside surface.
It is therefore a principal object of the present invention to provide an improved multilayered hollow plastic article and a method for obtaining same.
It is a further object of the present invention to provide an improved multilayered hollow plastic article wherein the inside layer terminates below the neck portion of the article.
It is a still further object of the present invention to provide an article and method which is economical and which represents significant savings of material in practice with desirable resultant properties.
Further objects and advantages of the present invention will appear hereinbelow.